The invention disclosed herein relates to an air admittance valve designed for connection to a pipe or duct where pressure excursions that are much greater than normal atmospheric pressure and which are lower than atmospheric pressure occur thus providing a need for the introduction of air from the outside of said duct or pipe via the valve without allowing the reverse flow of the air inside said duct or pipe when pressure in said pipe or duct is equalized or risen.
Sanitary drainage systems for buildings incorporate a network of pipes for conveying waste materials out of the building. At each point of conveyance most U.S. building codes require a certain water trap containing at the minimum requirement a two inch column of water which thereby prevents the passage of foul contaminated air into the building via the sanitary piping system. The primary reason that water seals in traps connected to said sanitary pipe must be protected is spent water discharged into the drainage system causes interaction with air at the air-water interface inside said pipe. A portion of the energy from the moving water is transferred to air setting it into motion. This flow of air at the core of said pipe in vertical drainage piping and at top of said pipe in horizontal branch piping generates a negative pressure excursion as it moves through the sanitary system. If said negative pressure exceeds the allowable limit defined by codes, water trap seal loss by siphonage will occur at an unacceptable level.
Air admittance valve devices are known (U.S. Pat. Nos. 3,923,081 and 4,232,706) for allowing air to enter sanitary pipework within buildings but prevent the passage of contaminated air outwardly from the piping system via the device during normal sanitary use conditions. These devices replace ventilation pipes and prevent said vent pipe from penetrating building structural components and ultimately the roofing membrane.
Technology in known art disclose various devices that rely on suitable elastomeric valve sealing members, said valve members rest against seats by the force of springs, weight or otherwise and open automatically when air is required in the sanitary piping system upon the force of vacuum. Valve sealing member is normally biased against valve seats, so when internal pressure is equalized within the piping system said valve member engages the seats thus prevents foul air from passing out therefrom.
The object and novelty of this invention is to provide a device capable of overcoming important problems associated with the practical installation and use of such air valves. The problems are as follows:
1. The valve mechanism must not fail when it is exposed to high pressure excursions, such as produced by testing the sanitary piping system with water, when said piping is filled, the resulting head pressure can exceed 50 pounds per square inch. PA1 2. The method by which the device is connected to the intended pipe must satisfy the national model building codes and high pressure, such as produced by equipment designed to clear blockages that can occur in said sanitary pipe system. PA1 3. The valve must be resistant to extreme atmospheric conditions which produce excessive pressure in building ventilation ducts resulting in undesirable reverse flow of fluid in said duct.
U.S. building codes require sanitary pipe systems to be tested prior to the installation of fixtures or appurtenances. e.g. water closet, lavatory, or sinks. The purpose of the test is to insure that all joints between pipes are indeed tight, so the inspector can certify system integrity under the applicable code assuring health and safety. One means of required test specifies a method by which all points of the drainage pipe network are to be subjected to minimum pressure that equals a ten foot column of water (4.33 p.s.i.). This mark being the minimum it is routine that the entire system is filled with water and resulting head pressure within the pipe can then exceed 50 p.s.i. However, the codes do not address maximum pressure regulations for said testing.
During the life of any sanitary system, it is highly probable that a drain blockage will occur at some point within said system. One way of clearing such an obstruction, includes a method that converts ordinary water into a powerful, directed force by means of a hydraulic pipeline flusher device. This equipment will produce pressure between 30 and 100 p.s.i. in a sudden burst.
Device sealing mechanisms disclosed in prior known art are particularly and inherently susceptible to high pressure failures caused by the examples above acting against disclosed elastomeric valve members said failure caused from inordinate distortion of said mechanism. Failure occurs when elastic sealing members disclosed deform under high pressure transmitted within the pipe to a point where valve seal breaches under said pressure. Said member when stretched by the force of pressure is forced downwardly and becomes trapped between the seats thus rendering the entire valve mechanism inoperable with said sealing member lodged to any extent. Contaminated fluid may then pass from the pipe via the device valve mechanism to surrounding atmosphere. Both instances of high pressure cited above occur everyday and the probability that an air valve will be subjected to the same is great.
The current invention solves the problem associated with the deformation of elastomeric materials described in prior art, caused by excessive pressure, by disclosing a more reliable device that is capable of resisting excessive internal pressure. The intended function of preventing contaminated air from within the sanitary system via the valve, is now shown to be more reliably and securely maintained.